Human tumors instigate granulin-expressing hematopoietic cells that promote malignancy by activating stromal fibroblasts in mice
Moshe Elkabets, … , Robert A. Weinberg, Sandra S. McAllister
Moshe Elkabets, … , Robert A. Weinberg, Sandra S. McAllister
Published January 25, 2011
Citation Information: J Clin Invest. 2011;121(2):784-799. https://doi.org/10.1172/JCI43757.
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Human tumors instigate granulin-expressing hematopoietic cells that promote malignancy by activating stromal fibroblasts in mice

Abstract

Systemic instigation is a process by which endocrine signals sent from certain tumors (instigators) stimulate BM cells (BMCs), which are mobilized into the circulation and subsequently foster the growth of otherwise indolent carcinoma cells (responders) residing at distant anatomical sites. The identity of the BMCs and their specific contribution or contributions to responder tumor growth have been elusive. Here, we have demonstrated that Sca1+cKit– hematopoietic BMCs of mouse hosts bearing instigating tumors promote the growth of responding tumors that form with a myofibroblast-rich, desmoplastic stroma. Such stroma is almost always observed in malignant human adenocarcinomas and is an indicator of poor prognosis. We then identified granulin (GRN) as the most upregulated gene in instigating Sca1+cKit– BMCs relative to counterpart control cells. The GRN+ BMCs that were recruited to the responding tumors induced resident tissue fibroblasts to express genes that promoted malignant tumor progression; indeed, treatment with recombinant GRN alone was sufficient to promote desmoplastic responding tumor growth. Further, analysis of tumor tissues from a cohort of breast cancer patients revealed that high GRN expression correlated with the most aggressive triple-negative, basal-like tumor subtype and reduced patient survival. Our data suggest that GRN and the unique hematopoietic BMCs that produce it might serve as novel therapeutic targets.

Authors

Moshe Elkabets, Ann M. Gifford, Christina Scheel, Bjorn Nilsson, Ferenc Reinhardt, Mark-Anthony Bray, Anne E. Carpenter, Karin Jirström, Kristina Magnusson, Benjamin L. Ebert, Fredrik Pontén, Robert A. Weinberg, Sandra S. McAllister

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Figure 5

GRN treatment mimics systemic instigation and results in responding tumor growth in vivo.

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GRN treatment mimics systemic instigation and results in responding tumo...
(A) Responding tumor incidence following injection and in situ treatment with rGRN protein at a high dose (250–2500 ng/ml) or low dose (2.5–25 ng/ml) or PBS control. Subcutaneous tumor sites were treated as indicated with 2 additional injections (n = 12 per group). (B) Average final mass of tumors represented in A. (C) Representative H&E staining of tumors treated with high or low dose of rGRN; cell nuclei stain dark purple. Scale bar: 100 μm. (D) Representative immunohistochemical staining of tumors treated with high or lose dose of rGRN. Serial tumor sections were stained for αSMA (red, left), mouse endothelial cell antigen (MECA32, brown, center), and Masson’s trichrome staining for collagen (blue, right). Scale bar: 50 μm. (E) Representative images used to quantify the extent of αSMA (red) incorporated into responding tumors that grew either opposite instigating tumors, in the presence of high or low dose rGRN, or with PBS control; cell nuclei were counterstained with hematoxylin (blue). Scale bar: 50 μm. Outlines show αSMA+ staining as identified by CellProfiler software (see Methods). (F) Graph shows average image area occupied by αSMA staining analyzed on a minimum of 25 images representing 5 tumors per group. (G) Growth of responding tumor cells in vitro during daily treatment with indicated doses of rGRN or PBS control. (H) Images of responding tumors resulting from either PBS control or high dose rGRN treatment and stained for proliferation marker Ki67 (brown); nuclei are counterstained with hematoxylin (blue). Original magnification, ×100. Data are expressed as mean ± SEM.